The present invention relates to an actuator for air duct damper in a car, and more particular to an actuator for air duct damper in a car with a new structure which allows a precise control on the flow of the air supplied in the indoor space of a car and which is improved in durability.
Generally in a car, air ducts 52 connected to a number of ejecting openings 51 in communication with the interior of a car are provided to supply into the indoor space of a car either the air heated or cooled by a heater 57 or an air conditioner evaporator 55 or the fresh outside air, as shown in FIG. 1. Further, the air ducts 52 are provided with a number of dampers 53 to control the flow of the air supplied to the respective ejecting openings 51, wherein the dampers 53 are adjusted in their degree of opening by respective actuators feed-back controlled.
A conventional actuator for adjusting the opening of an air duct damper comprises, as shown in FIG. 2, a driving motor 10 brought into rotation by a control section, a power transmitting mechanism 20 provided in a case 65 and connected to the driving motor 10 for transmitting a torque of the motor 10 to a damper 53, a connection terminal 61 provided at the power transmitting mechanism 20 and brought into rotation together with the power transmitting mechanism 20, a printed circuit board 60 attached on the case 65 and on which the connection terminal 61 is rotatable contacted. Further, as shown in Figure 3, a printed variable resistance band 63 is provided at the bottom of the printed circuit board 60 and connected to different circuit pattern in accordance with the change of the contact position of the connection terminal 61.
Therefore, when a passenger causes the transmission of a signal to the control section by operating an inputting section 63 installed on an instrument panel, the above-described driving motor 10 is brought into rotation in accordance with the signal of the control section, opening the damper 53 connected to the driving motor 10 through the power transmitting mechanism at a predetermined rotation angle. And, the connection terminal 61 is disposed on one side of the power transmitting mechanism 20 so as to be rotated together with the power transmitting mechanism 20, and the connection terminal 61 is rotated in contact with the variable resistance band 63, so that the feed back signal about the rotation angle of the damper 53 can be transmitted to the control section.
However, there is a problem with such an actuator in that the opening of a damper 53 is difficult to exactly control, when the resistance value becomes erroneous due to the deposition of a foreign material on the variable resistance band 63 or the connection terminal 61, the change in the temperature or the like, because the rotation angle indicating the duct opening is sensed as the variation in the resistance depending on the contacting location between the connection terminal 61 and the variable resistance band 63. There is another problem of the decreased durability of the commodities, because easy wear takes place with the repeated operation as the result of the tight contact operation between the connection terminal 61 and the variable resistance band 63.
Moreover, there is still other disadvantage of the need for a separate interface circuitry, because the analog resistance signal representing the opening of a damper, as sensed, needs to be converted to a corresponding digital signal in order to be used for the feed back control of the driving motor.
The present invention is intended to resolve the problem as described above and so the object of the invention is to provide an actuator for air duct damper in a car with a new structure, which allows a precise control on the flow of the air supplied in the indoor space of a car and which is improved in durability.
The above object is achieved according to the first feature of the invention by an actuator for car air duct damper including a driving motor 10 and a power transmitting mechanism 20 for transmitting the torque of the driving motor 10, said power transmitting mechanism 20 being provided at its final stage with a damper 53 for opening and closing air duct 52, wherein said actuator further comprises a rotary wheel 30 provided on and coaxial to the rotation shaft 54 of the damper 53, said rotary wheel being formed with a plurality of holes 33 along its circumference at a predetermined interval, optical sensors 40 disposed at the both side of the rotary wheel 30 closely so as to correspond to the holes 33, said optical sensors detecting the passage of the light through the holes 23, and a control section connected respectively to the optical sensors 40 and input button 63 in the indoor space of a car for controlling the driving motor 10 in accordance with respective input signals.
The above object is also achieved according to the second feature of the invention by an actuator for car air duct damper, wherein said power transmitting wheel 30 comprises either the final gear 25 of the power transmitting mechanism 20 directly formed with a plurality of holes 33 or a wheel formed with a plurality of holes 33, said wheel being provided separately from the final gear 25.
The above object is also achieved according to the third feature of the invention by an actuator for car air duct damper, wherein two or more concentric rows of holes 33a, 33b are formed in the circumferential area of said rotary wheel 30 in such a manner that the holes in an row are offset with regard to those in the neighboring row by a predetermined circumferential angle, and separate optical sensors 40a, 40b are disposed in locations corresponding to respective rows of holes 3a, 33b, so that the detection of rotating angle of the rotary wheel 30 can be made the more precisely with the increase in the rows of holes 33a, 33b. 
The above object is also achieved according to the forth feature of the invention by an actuator for car air duct damper, wherein a plurality of holes 33 are disposed on the whole 360xc2x0 periphery of the rotary wheel 30 by the predetermined interval, therefore the rotation angle can be sensed by said rotary wheel 30 and optical sensor 40 although said damper 53 is rotated as much as 360xc2x0 or more.